I just got the 70-200 4.0VRII, and I love it as well, shot sports this weekend and it was super. I used it on my new D7100 which I am getting used to as well. Reading this thread and seeing others comment on these cameras and the ability to get perfect focus is what I am experienceing, especially with the nikon 105mm attached. It seems that I just cannot use autofocus and get sharp enough results to submit here. I upgraded from the D300, and hardly ever had rejections for sharpness, but now I am afraid that I will. This is my first acceptance from my D7100, it is nice to be able to offer XXL.

Excuse me for being a bit late to the party on this one but I changed from D700 to D800 in the last week after prevaricating for a year. I think the difference is astonishing! Most of the time I use the 24-70 and 70-200 lens but I recently bought the 50mm 1.4 lens and first used the 800 with that attached. The depth and vibrancy of the images straight out of camera are incredible. It tests your technique for sure and the grab-shots from the hip that I love to take at weddings are a problem (as I found last Sunday!) but overall I am really pleased with the step-up. I loved my 700 but its definitely the spare body now.

I also moved up to a D800 from a D300s. The one thing that stands out to me other than some already mentioned above is the massive improvement in focus tracking. I shoot quite a bit of motorsport from time to time. With the D300 I reached the point of manually focusing on a point and waiting for the car to pass through it. This gave me a better shots / in-focus ratio over auto focus. With the D800 I can lock onto the car a good distance away and reliably track it right through the frame. I rarely have an out of focus motorsport shot these days.

As a newbie, I'd like to thank everybody for this interesting discussion. One tends to think that upgrading to a more expensive body will be "better" all the way around. But I hadn't thought of how an advanced sensor could highlight any deficiencies in whatever glass you attach to it, nor the changes it might force in one's approach to focus, use of tripod, etc. Not to mention the demands on your processing workflow.

I upgraded myself from a D300 to a D800. The first thing that really blew me away was the improved dynamic range.
And the absence of noise at night when compared to the D300 is astonishing. I had stopped shooting at night because the old good D300 just wasn't up to it any more.

I must admit that it took me a while to really appreciate all the improvements though. I guess that at first the wallet hole still hurt a lot - and please do not get me started on the wife

Just the fact that the d800 has a cmos sensor is enough reason to jump from d300 into d800, not counting iso performance and more mp. Actually I own a d800, a d700 and a d4 and I use 90 per cent of the time the d800, always for stock purposes.